Does mining waste concentration in the soil interfere with leaf selection by Acromyrmex subterraneus (Formicidae)?

Revegetation programs are proposed to recover the soil and biodiversity of disturbed sites, this being the case of the Rio Doce basin, Brazil. This region was hugely affected by a mining waste dam disruption, whose leakage on the soil altered its chemical and physical characteristics, and consequently the physiology and performance of plants. The expected alterations of the plants can make them more attractive for leaf-cutting ants, as lower water content induces an increase of non-structural carbohydrates. In this context, we evaluated whether Acromyrmex subterraneus workers differentiate among plants grown on soil with different mining waste concentrations. Leaf disks from plants grown in soil containing 0, 25, 50, 75, and 100% of mining waste were simultaneously offered to workers from laboratory ant colonies. The number of transported disks from each mining waste concentration was recorded until all disks of any concentration had been transported. Leaf selection assays were repeated after 30 days due to the novelty effect phenomenon. Leaf thickness, water, starch, and total soluble carbohydrates (TSC) contents were determined. Leaf disks from plants grown in soil with 100% of mining waste concentration were preferentially selected in both selection assays. Leaf thickness and water content were significantly lower in plants from the aforementioned treatment, while starch and TSC were higher. Results suggest that seedlings implanted in sites with high mining waste concentration are under high predation risk. Revegetation programs must measure the impact of leaf-cutting ants as both herbivorous and soil ecosystem engineers, for the best management of these insects. Abstract in Portuguese is available with online material

Automated summary

The study examined the impact of mining waste on planted vegetation and the leaf selection behavior of Acromyrmex subterraneus in soil with different mining waste concentrations. Results showed that seedlings planted in areas with high mining waste concentration are at high risk of predation by leaf-cutting ants.